在接手他人代码或调研一些开源项目时，如果能够理清其中的代码调用链路，这将加速我们对实现的理解。
本文介绍一款工具 go-callvis，它能够将 Go 代码的调用关系可视化出来，并提供了可交互式的 web 服务。
go-callvis 使用
依赖
-graphviz工具安装
go get -u github.com/ofabry/go-callvis
# or
git clone https://github.com/ofabry/go-callvis.git
cd go-callvis && make install
示例
package main
import (
func main() {
// Part 1: create a listener
l, err := net.Listen("tcp", ":8000")
if err != nil {
log.Fatalf("Error listener returned: %s", err)
}
defer l.Close()
for {
// Part 2: accept new connection
c, err := l.Accept()
if err != nil {
log.Fatalf("Error to accept new connection: %s", err)
}
// Part 3: create a goroutine that reads and write back data
go func() {
log.Printf("TCP session open")
defer c.Close()
for {
d := make([]byte, 1024)
// Read from TCP buffer
_, err := c.Read(d)
if err != nil {
log.Printf("Error reading TCP session: %s", err)
break
}
log.Printf("reading data from client: %s\n", string(d))
// write back data to TCP client
_, err = c.Write(d)
if err != nil {
log.Printf("Error writing TCP session: %s", err)
break
}
}
}()
}
}
以上是一个简单的TCP服务端代码，通过 go-callvis 工具，可将其代码调用关系梳理出来。
$ go-callvis main.go
2022/08/14 21:23:03 http serving at http://localhost:7878
2022/08/14 21:23:03 converting dot to svg..
2022/08/14 21:23:03 serving file: /var/folders/xk/gn46n46d503dsztbc6_9qb2h0000gn/T/go-callvis_export.svg
go-callvis 默认将代码调用关系存储成 svg 格式的图形，并会在 http://localhost:7878 服务上进行展示。
在浏览器界面上，如果点击 log 单元，将会进入 log 模块的代码调用交互图中。
使用参数
go-callvis 默认以 main 作为链路起点进行分析，因此 package 需要为 main 包。
go-callvis [flags] package
如果不想从 main 方法开始，那么需要使用 -tests 参数，并且在 yourpackage 下创建单元测试，在测试中调用你想要的起始点方法。
go-callvis -tests yourpackage
go-callvis$ go-callvis
go-callvis: visualize call graph of a Go program.
Usage:
go-callvis [flags] package
Package should be main package, otherwise -tests flag must be used.
Flags:
-algo string
The algorithm used to construct the call graph. Possible values inlcude: "static", "cha", "rta", "pointer" (default "pointer")
-cacheDir string
Enable caching to avoid unnecessary re-rendering, you can force rendering by adding 'refresh=true' to the URL query or emptying the cache directory
-debug
Enable verbose log.
-file string
output filename - omit to use server mode
-focus string
Focus specific package using name or import path. (default "main")
-format string
output file format [svg | png | jpg | ...] (default "svg")
-graphviz
Use Graphviz's dot program to render images.
-group string
Grouping functions by packages and/or types [pkg, type] (separated by comma) (default "pkg")
-http string
HTTP service address. (default ":7878")
-ignore string
Ignore package paths containing given prefixes (separated by comma)
-include string
Include package paths with given prefixes (separated by comma)
-limit string
Limit package paths to given prefixes (separated by comma)
-minlen uint
Minimum edge length (for wider output). (default 2)
-nodesep float
Minimum space between two adjacent nodes in the same rank (for taller output). (default 0.35)
-nodeshape string
graph node shape (see graphvis manpage for valid values) (default "box")
-nodestyle string
graph node style (see graphvis manpage for valid values) (default "filled,rounded")
-nointer
Omit calls to unexported functions.
-nostd
Omit calls to/from packages in standard library.
-rankdir string
Direction of graph layout [LR | RL | TB | BT] (default "LR")
-skipbrowser
Skip opening browser.
-tags build tags
a list of build tags to consider satisfied during the build. For more information about build tags, see the description of build constraints in the documentation for the go/build package
-tests
Include test code.
-version
Show version and exit.
[slp@slpdeMacBook-Pro:] ~/repo/MongoShake/cmd/collector $ go-callvis --help
Usage of go-callvis:
-algo string
The algorithm used to construct the call graph. Possible values inlcude: "static", "cha", "rta", "pointer" (default "pointer")
-cacheDir string
Enable caching to avoid unnecessary re-rendering, you can force rendering by adding 'refresh=true' to the URL query or emptying the cache directory
-debug
Enable verbose log.
-file string
output filename - omit to use server mode
-focus string
Focus specific package using name or import path. (default "main")
-format string
output file format [svg | png | jpg | ...] (default "svg")
-graphviz
Use Graphviz's dot program to render images.
-group string
Grouping functions by packages and/or types [pkg, type] (separated by comma) (default "pkg")
-http string
HTTP service address. (default ":7878")
-ignore string
Ignore package paths containing given prefixes (separated by comma)
-include string
Include package paths with given prefixes (separated by comma)
-limit string
Limit package paths to given prefixes (separated by comma)
-minlen uint
Minimum edge length (for wider output). (default 2)
-nodesep float
Minimum space between two adjacent nodes in the same rank (for taller output). (default 0.35)
-nodeshape string
graph node shape (see graphvis manpage for valid values) (default "box")
-nodestyle string
graph node style (see graphvis manpage for valid values) (default "filled,rounded")
-nointer
Omit calls to unexported functions.
-nostd
Omit calls to/from packages in standard library.
-rankdir string
Direction of graph layout [LR | RL | TB | BT] (default "LR")
-skipbrowser
Skip opening browser.
-tags build tags
a list of build tags to consider satisfied during the build. For more information about build tags, see the description of build constraints in the documentation for the go/build package
-tests
Include test code.
-version
Show version and exit.
每个参数都有对应的说明，无需详细介绍。
nostdgroupincludelimitignore总结
go-callvis 工具将 Go 程序函数调用关系通过图形可视化出来，它能帮助开发人员更好地梳理程序脉络。且 go-callvis 的使用非常简单，可以开箱即用。
之后同学们在接触复杂项目时，不妨用 go-callvis 试试看。